High temperature electrolyzer (hte) including a plurality of cells, having improved operation in the event of breakage of at least one cell and during ageing

Abstract

A process of electrolyzing water at high temperatures implemented by a cell stack reactor, including: a) simultaneously circulating water vapour at each cathode and at each anode as a leaching gas, temperatures of the water vapour at an inlet of each anode and each cathode being lower than high temperatures at which electrolysis is carried out and the water vapour circulating at the anode being at an overpressure with respect to the cathode; b) upon starting the electrolysis, supplying electrical power having a substantially constant electrical voltage across terminals of the stack and maintaining same. In event of breakage of one or more cells, complete destruction of the stack is avoided and high production efficiency is maintained, and efficiency is maintained during ageing.

1 - 8 . (canceled) 
     
     
         9 . A process of electrolyzing water at high temperatures implemented by an electrochemical reactor including a stack of elementary electrochemical cells each formed of a cathode, an anode, and an electrolyte inserted between the cathode and the anode, at least one interconnecting plate being arranged between two adjacent elementary cells and in electrical contact with an electrode of one of the two elementary cells and an electrode of the other of the two elementary cells, in which at least the water vapour is made to circulate in contact with the cathode and a leaching gas is made to circulate in contact with the anode to evacuate oxygen produced, the method comprising:
 a) simultaneously circulating the water vapour containing at most 1% of hydrogen at each cathode and at each anode as a leaching gas, temperatures of the water vapour at an inlet of each anode and each cathode being lower than high temperatures at which electrolysis is carried out, and the water vapour circulating at the anode being at an overpressure with respect to the cathode; and   b) imposing upon starting the electrolysis and maintaining a substantially constant level of electrical voltage across terminals of the stack of electrolysis cells.   
     
     
         10 . A process of electrolyzing water according to  claim 9 , wherein the overpressure of the water vapour containing at the most 1% of hydrogen at the anode compared to that at the cathode is between 5 and 100 mbars, or is 30 mbars. 
     
     
         11 . A process of electrolyzing water according to  claim 9 , wherein a number of elementary cells and a level of voltage imposed and maintained constant are such that unitary voltage across the terminals of each elementary cell is of an order of 1.3 volts. 
     
     
         12 . A process of electrolyzing water according to  claim 9 , wherein an initial conversion rate into hydrogen is of an order of 100%. 
     
     
         13 . A process of electrolyzing water according to  claim 9 , wherein a flow rate of water vapour at each cathode is increased, when a conversion rate into hydrogen initially determined at an outlet of each cathode drops. 
     
     
         14 . A process of electrolyzing water at high temperature according to  claim 9 , at temperatures of at least 450° C., or between 700° C. and 1000° C. 
     
     
         15 . A device for electrolyzing water at high temperatures, comprising:
 an electrical voltage source;   a reactor comprising a stack of elementary electrochemical cells each formed of a cathode, an anode, and an electrolyte inserted between the cathode and the anode;   at least one interconnecting plate being arranged between two adjacent elementary cells and in electrical contact with an electrode of one of the two elementary cells and an electrode of the other of the two elementary cells, the interconnecting plate comprising at least one cathodic compartment and at least one anodic compartment for circulation of gases respectively at the cathode and at the anode;   wherein one of ends of the cathodic compartments is connected to a supply configured to deliver water vapour containing at most 1% of hydrogen and one of ends of the anodic compartments is also connected to a supply configured to deliver water vapour containing at most 1% of hydrogen at an overpressure compared to those of the cathode, the supplies are configured to deliver the water vapour at temperatures below those at which the electrolysis is carried out; and   further comprising means connected to the electrical voltage source to deliver a substantially constant voltage across terminals of the two interconnecting plates of the stack furthest away from each other.   
     
     
         16 . An assembly for producing hydrogen comprising a plurality of devices according to  claim 15 .